recursive lambdas

[Sam Pullara]

The fact that this works for fields helps. I think we will want to
make it work for local variables in the future but it is nice that
this is possible right now.

Sam

On Mon, Sep 24, 2012 at 8:11 AM, Brian Goetz <brian.goetz at oracle.com> wrote:
> Yes, it works for fields but not for locals.  This is because the
> init-before-use rules for locals are stricter.
>
>
> On 9/24/2012 10:50 AM, Aleksey Shipilev wrote:
>>
>> Let me be more clear. As I understand the spec prohibits this:
>>
>>     void test() {
>>        IntUnaryOperator fib =
>>            (n) -> (n < 2) ? 1 : fib.operate(n - 1) + fib.operate(n - 2);
>>     }
>>
>> ...but still allows this (still a recursive lambda):
>>
>>     public IntUnaryOperator fib =
>>           (n) -> (n < 2) ? 1 : fib.operate(n - 1) + fib.operate(n - 2);
>>
>> ...because the current JLS does not prohibit this. Also, the plain old
>> inner classes work as well:
>>
>>      public IntUnaryOperator fib =
>>              new IntUnaryOperator() {
>>                  @Override
>>                  public int operate(int n) {
>>                      return (n < 2) ? 1 :
>>                           fib.operate(n - 1) + fib.operate(n - 2);
>>                  }
>>              };
>>
>>      public interface IntUnaryOperator {
>>          int operate(int v);
>>      }
>>
>>
>> Am I correct?
>>
>> Thanks,
>> Aleksey.
>>
>> On 09/24/2012 06:28 PM, Brian Goetz wrote:
>>>
>>> We decided to disallow this form for the time being, in part to simplify
>>> the metafactory protocol and therefore increase the chance of
>>> intrinsification of lambda capture sites.
>>>
>>> On 9/24/2012 10:01 AM, Aleksey Shipilev wrote:
>>>>
>>>> Hi guys,
>>>>
>>>> What is our current stance on recursive lambdas? I.e. should this code
>>>> considered to be correct?
>>>>
>>>>       public static IntUnaryOperator fib =
>>>>          (n) -> (n < 2) ? 1 : fib.operate(n - 1) + fib.operate(n - 2);
>>>>
>>>> The current EDR spec says nothing about this, except for "Remove support
>>>> for recursive lambdas" in the changelog, but both latest public b56 and
>>>> the nightly binary builds of lambda/lambda forest in OpenJDK do accept
>>>> this as the correct code.
>>>>
>>>> The reason I ask is that I keep bugging IDEA guys about their lambda
>>>> support, fixing a bug here, there, and everywhere, as this helps people
>>>> to start hacking on lambdas and provide the useful feedback:
>>>>      http://youtrack.jetbrains.com/issue/IDEA-91986
>>>>
>>>> I think everyone realizes the spec is in flux, but it is important to
>>>> understand what are we leaning towards.
>>>>
>>>> Thanks,
>>>> Aleksey
>>>>
>>
>